The present invention relates to apparatus and method for the detection of the vectorial direction of rotation of a multiphase AC voltage power supply. It is more particularly applicable to sensing the direction of rotation of an AC motor in a motor drive.
Rather than sensing the direction of rotation of the motor, it is known in a motor drive to rely upon the rotation of the three-phase voltage at the input of the AC motor. This has been done in the past with counters providing an indication of the magnitude of the voltages in the respective phases as a function of the electrical angle, and the counts so derived were used to effect calculations providing a reference for comparison with the running phase counts and determine phase rotation. In contrast with previous practice, it is now proposed to effect simultaneous readings with counters associated with the current phase voltages and derive directly from such counts, and instantaneously, information relative to the sequence of the phases.